1. Technical Field
The present invention relates to a real-time global illumination rendering system in which artifacts are suppressed by estimating appropriate specular roughness using sampling results and performing shading using the estimated specular roughness.
2. Related Art
In computer graphics, in order to determine brightness of an object close to the actual one, rendering by global illumination (GI) is performed. The global illumination is an illumination calculation taking into account not only a direct light component from a light source, but also an indirect light component. To represent in which direction and at what intensity the indirect light is reflected, a bidirectional reflectance distribution function (BRDF) is used.
In global illumination, as a method for determining an indirect light component, there is known final gathering (HACHISUKA, T. 2005. High-quality global illumination rendering using rasterization. In GPU Gems 2. Addison-Wesley Professional, ch. 38, 615-634). Final gathering is a method for determining an indirect light component by tracing a plurality of rays.
In addition, as a technique for determining an indirect light component, there is known an instant radiosity method using a virtual point light source (KELLER, A. 1997. Instant radiosity. In ACM SIGGRAPH '97, 49-56). As a technique for tracing rays in the same direction at a time, there are ray-bundles.
To represent in which direction and at what intensity light is reflected, a bidirectional reflectance distribution function (BRDF) is proposed. Examples of already-known BRDF models include a Lambert model representing diffuse reflection, a Phong model representing specular reflection, a Blinn model, and a Cook-Torrance model.